Headspace Analysis Conditions - Essay Example

The vial is placed in line with a gas chromatography column, the vial heated and the vaporized sample swept on the column and the components separated. This technique has been used to identify spoiled food, fragrances from botanical material, the determination of plasticizers in plastics and forensic samples involving arson snuff. Its main component, nicotine is habit-forming and other compounds produced by pyrolysis during smoking are carcinogenic and can cause several other health problems. Tobacco is an extremely valuable export in the United States despite the health concern, and its quality is carefully monitored. Tobacco can be flue-cured, air-cured, fire-cured, or sun-cured, but the quality of the product can often be monitored by analyzing the vapours in the headspace above the tobacco. The headspace over tobacco can be sampled and analyzed using a Solid Phase Micro Extraction (SPME) technique.

Diesel is similar in chemical composition to kerosene and heating oil in that it is composed of aliphatic hydrocarbons that are obtained from the fractional distillation of crude oil. Diesel has a higher boiling point fraction and the distillation range is greater than that of kerosene and heating oil being composed of essentially C10 to C25 aliphatic hydrocarbons.

Dynamic headspace sampling with Capillary G.L.C. analysis will successfully analyse fire debris for accelerants and is capable of detecting a microlitre of accelerant.

The use of these extremely sensitive laboratory techniques must be made carefully because of the consequence of obtaining a false positive result. The possibility of the accidental contamination of a sample through poor sampling and laboratory techniques needs to be minimized.

The research has shown the sample containers can be cleaned before use and should be sealed before transport to the fire scene. Samples should then be delivered to the laboratory and analysed promptly. The laboratory equipment should be cleaned before use and blank samples analysed regularly to check for any possible contamination.  The extraction equipment can be cleaned by washing it with acetone and heating the gas transfer lines with a Bunsen burner. The interpretation of the chromatograms must be made carefully using a library of chromatograms composed of common accelerants, industrial solvents, and common household materials.

The analysis of numerous burnt synthetic materials was found to be distinct from the common accelerants. The common accelerants were found to change during evaporation making it sometimes difficult to distinguish between those composed entirely of entirely of an aliphatic hydrocarbon fraction. Ethanol could not be detected in fire debris using charcoal absorption extraction techniques and alternative analytical techniques were needed.

The background level of accelerants in the environment is dependent on the history of the sample material. Traces of petrol and aliphatic hydrocarbons were found in soil from a motor wrecking yard, however, no traces were found in numerous car flooring materials indicating none would be expected from a domestic environment. Gas odourants could also be detected using the same equipment as that used for fire debris analysis which would assist in the investigation of suspected gas explosions.